The present description relates to a vehicle brake system for a land vehicle, which for example enables regenerative braking, i.e. a braking operation, in which an electric machine converts kinetic energy of the land vehicle to electrical energy.
Vehicles as a rule have a vehicle brake system, in which for the purpose of braking a hydraulic fluid is conveyed to wheel brakes of a vehicle. Increasingly, however, vehicles also have an electric machine that is used at least as assistance to an internal combustion engine to drive the vehicle. Compared to an internal combustion engine the electric machine offers the advantage that it may be operated regeneratively during the so-called regenerative braking in order to charge a vehicle battery. The chemical energy stored in the charged battery is then used during a motorised operation of the electric machine to drive the motor vehicle.
Whereas during normal braking kinetic energy of the vehicle is converted to thermal energy because of the frictionally engaged interacting of brake shoes and brake discs at the wheel brakes, what occurs during regenerative braking is therefore a charging of the vehicle battery. Since during regenerative braking the deceleration of the motor vehicle is effected by means of the electric machine, the wheel brakes may remain unactuated. As a rule this is even desirable because any kinetic energy converted to thermal energy at the wheel brakes is no longer available for charging the vehicle battery.
So, for example the document DE 10 2009 039 207 A1 describes a regenerative vehicle brake and an operating method for a regenerative vehicle brake, which has a regeneration device that enables an asymmetric regenerative braking operation for a first and a second hydraulic brake circuit. A vehicle having such a regenerative vehicle brake comprises a generator, wherein during the regenerative braking operation a brake pressure build-up at wheel brakes of the first brake circuit occurs at least in a reduced manner and a brake pressure build-up at wheel brakes of the second brake circuit occurs in a substantially unreduced manner. For this purpose the regeneration device comprises at least delay devices.
The vehicle brake described in document DE 10 2009 039 207 A1 however comprises more components than conventional brake systems. These additional components take up additional installation space and increase the system weight. What is more, pedal-reaction simulating devices that are used with regenerative vehicle brakes often entail a more complicated control of the brake system or exhibit partially an unsatisfactory control quality.
It would moreover be desirable for the vehicle brake system to be suitable for conventionally braked land vehicles and regeneratively braked land vehicles, or to be at least relatively easily adaptable to the respective requirements.